CN115369317A

CN115369317A - Nickel-plated and zinc-plated hot-formed steel plate, preparation method thereof and preparation method of hot-formed part

Info

Publication number: CN115369317A
Application number: CN202210644511.1A
Authority: CN
Inventors: 张博明; 徐德超; 赵海峰; 王彭涛; 滕华湘; 韩赟; 李研; 张士杰; 王振鹏
Original assignee: Shougang Group Co Ltd; Shougang Jingtang United Iron and Steel Co Ltd
Current assignee: Shougang Group Co Ltd; Shougang Jingtang United Iron and Steel Co Ltd
Priority date: 2022-06-08
Filing date: 2022-06-08
Publication date: 2022-11-22

Abstract

The invention belongs to the field of coated steel plates, and particularly relates to a nickel-plated and zinc-plated hot-formed steel plate and a preparation method thereof as well as a preparation method of a hot-formed part. The hot-formed steel sheet includes: the hot forming steel plate comprises a hot forming steel plate substrate, a zinc layer and a metal nickel layer, wherein the zinc layer covers the hot forming steel plate substrate, and the metal nickel layer covers the zinc layer; by forming a Zn-Ni alloy, the melting point of the plating layer is increased during hot forming, thereby inhibiting cracks from extending to the substrate; in the subsequent hot forming process, the Zn-Ni alloy in the coating is still in a solid state at the hot forming temperature, so that the phenomenon of liquid crack brittleness is inhibited, the forming temperature range is expanded, and the production difficulty is reduced.

Description

Nickel-plated and zinc-plated hot-formed steel plate, preparation method thereof and preparation method of hot-formed part

Technical Field

The invention belongs to the field of coated steel plates, and particularly relates to a nickel-plated and zinc-plated hot-formed steel plate and a preparation method thereof as well as a preparation method of a hot-formed part.

Background

The new energy automobile industry is developed vigorously, and along with the gradual improvement of the requirement on the endurance of the new energy automobile, higher requirements are put forward for the light weight of an automobile body. Further, the demand for collision safety has also increased year by year, and these are all in need of starting from the design of the vehicle body. The use proportion of the high-strength steel on the body-in-white is improved, so that the effect of reducing the weight of the body can be achieved, and the collision safety of the body can be improved.

Currently, advanced High Strength Steels (AHSS) commonly used on vehicle bodies include: low alloy high strength steel (HSLA), DP steel, CP steel, hot formed steel, and the like. The hot forming steel is the single steel grade with the largest dosage on the body-in-white, and the dosage of the hot forming steel on the mainstream vehicle type is more than 15 percent, so the domestic hot forming steel is also rapidly developed. At present, the hot forming steel is generally 1500MPa grade, but with the rapid development of the related technologies such as integrated door rings and the like, the strength grade of the hot forming steel is extended to 500MPa-2000MPa. There are some problems in hot forming for non-plated hot formed steels, such as: protective gas needs to be introduced into the heating furnace, iron scale can be generated in the forming process, a decarburized layer can be generated in the heating process of the material, the performance is affected, and the formed parts need to be subjected to shot blasting and the like. At present, a hot forming steel material with a coating is commonly used, the largest amount of the hot forming steel with the Al-Si coating is used, the Al-Si coating has excellent high temperature resistance, no oxide scale is generated in the hot forming process of the material, and shot blasting is not needed after production. However, the poor corrosion resistance of Al-Si coatings only serves as a physical corrosion protection, and pure zinc coated hot formed steels are receiving increasing attention.

Pure zinc coatings have excellent corrosion resistance and, even after hot forming, still have a cathodic protection effect, but they have disadvantages such as: liquid zinc is easy to crack and cause brittleness (LME) and the like, and the development of pure zinc hot forming steel is restricted. At present, an indirect hot forming technology is commonly used for pure zinc hot forming steel, materials are pre-deformed by about 90% at room temperature, then conventional hot forming heating and forming are carried out, LME is reduced by reducing deformation of hot forming, but two punching devices are needed for indirect forming, production cost and maintenance cost are increased, and production rhythm is slowed down.

Patent CN 112779474A, a hot forming strip steel of 2000MPa grade of zinc-based plating and a production method thereof disclose a hot forming strip steel of 2000MPa grade of zinc-based plating and a production method thereof, and the used substrate comprises the following components (wt%): c:0.25-0.4, mn:1.1-1.7, S is less than or equal to 0.012 percent, P is less than or equal to 0.02 percent, si:0.1-0.3%, al:0.03-0.05%, cr:0.2-0.4, B: 0.001-0.003%, ti:0.035-0.05%, V:0.15-0.3 percent of N, and less than or equal to 0.0030 percent of N. In the patent, a large amount of V element is added for improving the elongation of the material, so that the cost and the production difficulty of the material are greatly improved. In addition, tempering treatment is required for 5-30min after the materials in the patent are subjected to hot forming, so that the production rhythm is seriously slowed down, and the production cost is increased.

Patent CN 112170662A, hot forming process of zinc-based coated high-strength steel discloses a hot forming process of zinc-based coated high-strength steel, which comprises the following process steps: heating the galvanized sheet to 500-600 ℃ in an inert atmosphere, preserving heat for 3-5min, heating to substrate austenitizing temperature, preserving heat to complete austenitizing, then discharging from the furnace, cooling to 600-700 ℃ at a cooling speed of 30-50 ℃/s, transferring to a stamping and shaping die, and performing pressure-maintaining quenching treatment at the quenching temperature of 450-650 ℃ and the quenching cooling speed of 30-50 ℃/s. The LME cracks can be reduced or inhibited by adopting the hot forming process, but the process needs two-stage heating, the integral heating time is longer, and protective atmosphere needs to be introduced in the heating process. In addition, precooling is required after discharge, which increases the production difficulty and the requirement on equipment and increases the production cost.

Disclosure of Invention

The application provides a nickel-plated and zinc-plated hot-formed steel plate, a preparation method thereof and a preparation method of a hot-formed part, and aims to solve the technical problem that liquid cracks on the surface of the zinc-plated hot-formed steel plate are fragile.

In a first aspect, the present application provides a nickel-plated, zinc-plated, hot-formed steel sheet comprising: the hot forming steel plate comprises a hot forming steel plate substrate, a zinc layer and a metal nickel layer, wherein the zinc layer covers the hot forming steel plate substrate, and the metal nickel layer covers the zinc layer.

Optionally, the thickness of the zinc layer is 5 μm to 15 μm.

Optionally, the components of the hot-formed steel plate substrate include: and C:0.05% -0.25%, mn:1% -4%, al:0.05% -1%, si:0.2% -0.5%, cr:0.05% -0.25%, V:0.01% -0.1%, ti:0.01% -0.1%, B:0.0015% -0.004%, P:0-0.005%, N:0-0.005%, S:0 to 0.005% and the balance of Fe and inevitable impurities.

Optionally, the zinc layer comprises the following components: in mass fraction, al: 0.05-0.25%, and the balance of Zn and inevitable impurities.

In a second aspect, the present application provides a method for producing the nickel-plated zinc-plated hot-formed steel sheet described in the first aspect, the method comprising the steps of:

obtaining an annealed steel plate;

carrying out hot galvanizing and first cooling on the annealed steel plate to obtain a hot galvanized steel plate;

carrying out nickel electroplating treatment on the hot-dip galvanized steel plate to obtain a nickel-plated steel plate;

and finishing and curling the nickel-plated steel plate to obtain the hot-formed steel plate.

Optionally, in the electroplating nickel treatment, the current density is 40A/dm ² -80A/dm ² The thickness of the single-side electroplating layer is 200nm-1 μm.

Optionally, the temperature of a zinc pot for hot galvanizing is 430-470 ℃, and the time for hot galvanizing is 2-6 s.

Optionally, the end point temperature of the first cooling is less than or equal to 200 ℃.

In a third aspect, the present application provides a method for preparing a nickel-plated and zinc-plated thermoformed article, including the steps of: the nickel-plated and zinc-plated hot-formed steel sheet according to the first aspect or the nickel-plated and zinc-plated hot-formed steel sheet obtained by the method according to the second aspect is subjected to hot forming treatment to obtain a target hot-formed article.

Optionally, the thermoforming treatment includes heating, transferring, holding pressure, and second cooling, the target temperature of the heating is 880 ℃ to 950 ℃, and the heating time is 3min to 6min.

Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:

the hot-formed steel sheet provided by the embodiment of the present application includes: the hot forming steel plate comprises a hot forming steel plate substrate, a zinc layer and a metal nickel layer, wherein the zinc layer covers the hot forming steel plate substrate, and the metal nickel layer covers the zinc layer; because the metal nickel layer is positioned on the surface of the zinc layer, ni element can be quickly diffused into the zinc layer to generate Zn-Ni alloy in the subsequent austenitizing heating process so as to improve the melting point of the plating layer, and because the metal nickel layer is positioned on the surface of the zinc layer, the diffusion of nickel into the substrate can be reduced in the heating process, and the content of nickel in the plating layer is improved; by forming a Zn-Ni alloy, the melting point of the plating layer is increased during hot forming, thereby inhibiting cracks from extending to the substrate; in the subsequent hot forming process, the Zn-Ni alloy in the coating is still in a solid state at the hot forming temperature, so that the phenomenon of liquid crack brittleness is inhibited, the forming temperature range is expanded, and the production difficulty is reduced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a schematic flow chart of a method for preparing a nickel-plated and zinc-plated hot-formed steel plate according to an embodiment of the present application;

FIG. 2 is an EDS analysis of the surface of a hot formed part provided in example 1 of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making creative efforts shall fall within the protection scope of the present application.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. For example, room temperature may refer to a temperature in the interval 10 to 35 ℃.

Unless otherwise specifically indicated, various raw materials, reagents, instruments, equipment and the like used in the present invention may be commercially available or may be prepared by existing methods.

According to an exemplary embodiment of the present invention, there is provided a nickel-plated and zinc-plated hot-formed steel sheet including: the hot forming steel plate comprises a hot forming steel plate substrate, a zinc layer and a metal nickel layer, wherein the zinc layer covers the hot forming steel plate substrate, and the metal nickel layer covers the zinc layer.

In the embodiment of the application, in the hot forming process, the Ni element can be rapidly diffused to the zinc layer to generate Zn-Ni alloy, so that the melting point of the coating can be improved, the crack is prevented from extending to the substrate, and the phenomenon of brittleness caused by liquid cracks is avoided. Specifically, the melting point of Zn-Ni alloy is around 880 ℃ while that of Zn-Fe alloy is only 780 ℃. By forming Zn-Ni alloy, the plating layer can be ensured to be still in a solid state at the forming temperature of 700-800 ℃, thereby inhibiting the occurrence of LME phenomenon.

In addition, a metallic nickel layer on the surface of the hot-dip galvanized steel sheet can improve the surface quality of the steel sheet and replace oil coating treatment after plating; compared with zinc, the metal nickel has higher hardness, and can avoid the material from being scratched and scratched in the transportation process; because the metal nickel layer is attached to the surface of the zinc layer in an electroplating way, the nickel can fill gullies on the surface of the plating layer, so that the surface of the plating layer is smoother and favorable for the subsequent blanking process;

in some embodiments, the zinc layer has a thickness of 5 μm to 15 μm.

The thickness of the zinc layer is controlled to be 5-15 mu m, so that the completeness of Ni diffusion can be effectively improved; the zinc layer is too thick, so that Ni is not completely diffused and the zinc layer is continuously thickened after heating, and cracks are easily generated in the stamping process along with the increase of the thickness; too thin a zinc layer can result in a material with reduced corrosion resistance.

In some embodiments, the components of the thermoformed steel sheet substrate comprise: and C:0.05% -0.25%, mn:1% -4%, al:0.05% -1%, si:0.2% -0.5%, cr:0.05% -0.25%, V:0.01% -0.1%, ti:0.01% -0.1%, B:0.0015% -0.004%, P:0-0.005%, N:0-0.005%, S:0 to 0.005% and the balance of Fe and inevitable impurities.

The role of each component of the hot forming steel plate substrate is as follows:

c:0.05 to 0.25 percent, and C is a main component in the steel, mainly plays a role in adjusting the strength grade of the hot forming steel, and can stabilize austenite, but the C content is too large to cause a series of problems such as plasticity reduction and welding performance reduction, so the C content is controlled.

Mn:1% -4%, mn mainly plays a role in solid solution strengthening, and can reduce the austenitizing temperature of the material and improve the hardenability of the material.

Al: 0.05-1 percent, and the Al mainly has the function of refining grains and improving the low-temperature toughness and the elongation of the material.

Si: 0.2-0.5%, and Si is mainly used for inhibiting the precipitation of cementite and stabilizing austenite.

Cr: 0.05-0.25 percent, and Cr is used for improving the hardenability and the tempering stability of the steel and ensuring that the part has good comprehensive mechanical properties after being directly formed or formed and tempered.

V: 0.01-0.1%, and the addition of a small amount of V can improve the thermal stability of the substrate, refine the crystal grains of the substrate in the austenitizing process, and improve the tempering stability of martensite.

Ti:0.01% -0.1%, the main function is to refine austenite grains, and the austenite grains are combined with C and N to form a precipitate to play a role of fixing N.

B:0.0015 to 0.004 percent, and B is a main element in the hot forming steel, mainly plays a role in improving the hardenability of the material and ensures the strength grade of the formed material.

In some embodiments, the composition of the zinc layer comprises: in terms of mass fraction, al:0.05 to 0.25 percent, and the balance of Zn and inevitable impurities.

Controlling the ratio of Al: the reason for 0.05% to 0.25% is that: the Al element is added into the plating solution to generate a restraining layer on the surface of the substrate so as to control the thickness of the plating layer, and if the content of the aluminum is not in the range, the thickness of the plating layer exceeds the patent limit range, and the service performance of the material is influenced.

In a second aspect, the present application provides a method of producing the nickel-plated zinc-plated hot-formed steel sheet of the first aspect, as shown in fig. 1, the method including the steps of:

s1, obtaining an annealed steel plate;

s2, carrying out hot galvanizing and first cooling on the annealed steel plate to obtain a hot galvanized steel plate;

s3, carrying out nickel electroplating treatment on the hot-dip galvanized steel plate to obtain a nickel-plated steel plate;

and S4, finishing and curling the nickel-plated steel plate to obtain the hot-formed steel plate.

Specifically, the annealed steel plate is obtained after molten iron is subjected to pretreatment, converter smelting, alloy fine adjustment, LF furnace refining, continuous casting, hot rolling, cold rolling and annealing. In the hot rolling process, the discharging temperature of the casting blank is 1100-1250 ℃, and the final rolling temperature is above 850 ℃. The hot rolled coil is subjected to acid cleaning and then cold rolling, and the cold rolling reduction is 50-80%; carrying out continuous annealing treatment, wherein the continuous annealing temperature is controlled to be between 750 and 880 ℃, the continuous annealing time is controlled to be between 150 and 300 seconds, the dew point temperature is controlled to be between-20 and 5 ℃, and the atmosphere in the annealing furnace is as follows (according to the volume percentage): 3% -8% of H ₂ The balance being N ₂ And then cooling to 450-490 ℃ at a cooling speed of 10-50 ℃/s to obtain the annealed steel plate.

By the method, the obtained hot-formed steel plate is stored in a steel coil form without being coated with oil or passivated; the mechanical properties of the hot formed steel sheet include: tensile strength: 550MPa-1200MPa, yield strength: 300MPa-1000MPa, elongation after fracture A50:12 to 30 percent.

In some embodiments, the current density in the electronickelling process is 40A/dm ² -80A/dm ² The thickness of the single-side electroplating layer is 200nm-1 μm.

Controlling the current density in the electro-nickelling treatment to be 40A/dm ² -80A/dm ² The reason for this is that: the current efficiency is optimal when the current density is used, and if the current density is not in the range, the current efficiency is reduced to cause energy waste; the reason why the thickness of the single-sided plating layer is controlled to be 200nm to 1 μm is that: when the thickness of the electroplating layer exceeds 1 μm, the uneven distribution of the thickness of the electroplating layer easily causes surface defects, and if the thickness of the single-side electroplating layer is less than 200nm, the melting point of the electroplating layer cannot be effectively improved.

In some embodiments, the hot galvanizing pot temperature is 430-470 ℃, and the hot galvanizing time is 2-6 s.

The reason why the temperature of a zinc pot for hot galvanizing is controlled to be 430-470 ℃ and the time of the hot galvanizing is controlled to be 2-6 s is that: when the hot dipping time is controlled within 2s-6s, the adhesive force of the plating layer can be improved, thereby improving the service performance of the plating layer.

In a third aspect, the present application provides a method for preparing a nickel-plated and zinc-plated thermoformed piece, the method comprising the steps of: and (3) carrying out hot forming treatment on the nickel-plated and zinc-plated hot-formed steel plate or the nickel-plated and zinc-plated hot-formed steel plate prepared by the method in the first aspect to obtain the target hot-formed piece.

In the embodiment of the present application, the mechanical properties of the hot formed part include: tensile strength: 800MPa-1500MPa, yield strength: 400MPa-1100MPa, and 9% -20% of elongation A50 after fracture.

In some embodiments, the thermoforming process comprises heating, transferring, holding pressure, and a second cooling, the heating having a target temperature of 880 ℃ to 950 ℃, the heating for a time of 3min to 6min.

The heating time is controlled within 3min-6min, so that the Ni element can be effectively and completely diffused to the zinc layer; too long heating time can cause excessive Fe element to diffuse into the coating layer to cause the plasticity of the coating layer to be reduced, thereby causing cracking; short heating times can result in incomplete austenitization of the substrate affecting post-forming properties.

Specifically, the thermoforming process comprises: transferring for 3-7 s, maintaining for 8-15 s, cooling to below 200 deg.C, and demolding. Wherein, the atmosphere of the heating furnace is air, and the dew point is less than or equal to-20 ℃.

The process of the present invention will be described in detail below with reference to examples, comparative examples and experimental data.

The application provides a nickel plating zinc-plating hot formed steel sheet, hot formed steel sheet includes: the hot forming steel plate comprises a hot forming steel plate substrate, a zinc layer and a metal nickel layer, wherein the zinc layer covers the hot forming steel plate substrate, and the metal nickel layer covers the zinc layer; the thickness of the zinc layer is 5-15 μm. The chemical compositions of the thermoformed steel sheet substrates in examples and comparative examples are shown in table 1, and the nickel electroplating process and the zinc electroplating process are shown in table 2; the thermoforming process is shown in table 3;

table 1 chemical composition table (balance Fe and unavoidable impurity elements) of the substrates of examples 1 to 4 and comparative examples 1 to 3.

Serial number	C	Mn	Al	Si	Cr	V	Ti	B
									Example 1	0.05	1	0.05	0.2	0.05	0.01	0.01	0.0015
Example 2	0.1	2	0.2	0.3	0.1	0.03	0.03	0.002
									Example 3	0.2	3	0.5	0.4	0.2	0.05	0.06	0.003
Example 4	0.25	4	1	0.5	0.25	0.1	0.1	0.004
									Comparative example 1	0.3	5	0.5	0.4	0.2	0.05	0.06	0.003
Comparative example 2	0.2	3	0.5	0.4	0.2	0.05	0.06	0.003
									Comparative example 3	0.2	3	0.5	0.4	0.2	0.05	0.06	0.003

Table 2 table of nickel electroplating process and zinc electroplating process under different examples.

Table 3 thermoforming process under different examples.

Table 4 mechanical properties and crack depth tables before and after forming under different examples.

The invention provides a preparation method of a galvanized hot-formed steel plate with an electroplated nickel layer, which comprises the following steps:

s1, obtaining an annealed steel plate;

The method specifically comprises the following steps:

1) According to the components of the base plate shown in the table 1, the balance of Fe and inevitable impurities are subjected to molten iron pretreatment, converter smelting, alloy fine adjustment, LF furnace refining, continuous casting, hot rolling and cold rolling to obtain the medium manganese steel base plate for hot-dip aluminum silicon. Wherein, in the hot rolling process, the tapping temperature of the casting blank is 1100-1250 ℃, and the finishing temperature is above 850 ℃. And (3) pickling the hot rolled coil, and then carrying out cold rolling, wherein the cold rolling reduction is 50-80%.

2) And (2) carrying out continuous annealing treatment on the cold-rolled substrate, wherein the continuous annealing temperature is controlled to be between 750 and 880 ℃, the annealing time is controlled to be between 100 and 200 seconds, the dew point temperature in the annealing furnace is controlled to be between-20 and 5 ℃, and the atmosphere in the annealing furnace is (by volume percentage): 3% -8% of H ₂ The balance being N ₂ . Then cooling to 450-490 ℃ at a cooling speed of 10-50 ℃/s, wherein the temperature of the zinc pot and the hot-dipping time are shown in the table 2. After plating, the steel sheet was cooled to 200 ℃ or lower at a constant cooling rate to obtain hot-dip galvanized steel sheets as shown in Table 4.

3) And then carrying out an electroplating nickel process, and putting the cooled hot-dip galvanized steel plate into an electroplating liquid tank for electroplating, wherein the current density and the electroplating time are shown in the table 2.

4) And (3) rolling into a steel coil after finishing, straightening and adjusting the shape, and then shearing and blanking to obtain the material sheet for producing parts.

5) The thermoforming process shown in Table 3 was used to form a material whose physical and chemical properties are shown in Table 4, and FIG. 2 is a surface view of the thermoformed article obtained in example 1.

From comparative example 1, it can be seen that the tensile strength and yield strength of the substrate were improved but the elongation was decreased after the addition of excess C and Mn, and the subsequent process was the same as example 3 but the crack depth was 5 μm after forming, indicating that the elongation before and after forming of the substrate had an effect on the generation of cracks during forming.

From comparative example 2, it can be seen that the same composition, hot-dipping process and hot-forming process as in example 3 were employed, but the crack depth after hot-forming was 8 μm, indicating that the plating layer thickness was thin when the plating current density was small, and that the amount of Ni diffused into the plating layer during heating was small and the melting point of the plating layer could not be effectively increased, so that cracks were generated during forming.

As can be seen from comparative example 3, the hot dipping time was different from that of example 3, the thickness of the single-sided zinc layer was 22 μm, and the rest of the process was the same as that of example 3. As a result, when the thickness of the plated layer was excessively thick, ni could not be uniformly distributed in the plated layer, and the thickness of the plated layer continued to increase during heating, and the excessively thick Zn-Fe alloy layer increased the risk of cracking, so that the crack depth increased to 10 μm in comparative example 3.

Detailed description of the drawings fig. 2:

as shown in FIG. 2, a surface view of a hot-formed article obtained in example 1, in which the Ni element content in the surface was high after hot forming, and the element content at each position in the view is shown in the following table, it is explained that the Ni element at the surface and the Zn element form a Zn-Ni alloy during heating.

One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:

(1) The melting point of the plating layer can be improved by electroplating a layer of metal nickel on the surface of the pure zinc plating layer, so that the phenomenon of LME in the hot forming process is reduced and inhibited.

(2) The traditional passivation and oiling treatment can be replaced by electroplating nickel, so that the discharge of pollutants is reduced, and the environment is protected.

(3) The surface quality and the corrosion resistance of the galvanized hot forming steel can be improved by electroplating nickel, and the subsequent use is facilitated. In conclusion, the method can lighten and inhibit LME cracks in the direct hot forming process, replace oiling and passivating treatment after hot dipping, and improve the surface quality and corrosion resistance of the galvanized steel sheet.

It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.

The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A nickel-plated zinc-plated hot-formed steel sheet, characterized by comprising: the hot forming steel plate comprises a hot forming steel plate substrate, a zinc layer and a metal nickel layer, wherein the zinc layer covers the hot forming steel plate substrate, and the metal nickel layer covers the zinc layer.

2. A hot-formed steel sheet according to claim 1, wherein the thickness of the zinc layer is 5 μ ι η to 15 μ ι η.

3. The thermoformed steel sheet according to claim 1, wherein the composition of the thermoformed steel sheet substrate comprises: and C:0.05% -0.25%, mn:1% -4%, al:0.05% -1%, si:0.2% -0.5%, cr:0.05% -0.25%, V:0.01% -0.1%, ti:0.01% -0.1%, B:0.0015% -0.004%, P:0-0.005%, N:0-0.005%, S:0 to 0.005%, and the balance of Fe and unavoidable impurities.

4. A hot-formed steel sheet according to claim 1, wherein the composition of the zinc layer comprises: in mass fraction, al: 0.05-0.25%, and the balance of Zn and inevitable impurities.

5. A method of producing a nickel-and-zinc-plated hot-formed steel sheet according to any one of claims 1 to 4, characterized by comprising the steps of:

obtaining an annealed steel plate;

6. The method according to claim 5, wherein the current density in the electrolytic nickel plating treatment is 40A/dm ² -80A/dm ² The thickness of the single-side electroplating layer is 200nm-1 μm.

7. The method according to claim 5, wherein the hot galvanizing pot temperature is 430-470 ℃, and the hot galvanizing time is 2-6 s.

8. The method according to claim 5, characterized in that the end temperature of the first cooling is ≦ 200℃.

9. A method for preparing a nickel-plated and zinc-plated thermoformed piece is characterized by comprising the following steps: a nickel-plated and zinc-plated hot-formed steel sheet according to any one of claims 1 to 4 or a nickel-plated and zinc-plated hot-formed steel sheet obtained by the method according to any one of claims 5 to 8 is subjected to hot-forming treatment to obtain a target hot-formed article.

10. The method according to claim 9, wherein the thermoforming process comprises heating, transferring, holding pressure and a second cooling, the target temperature of the heating is 880 ℃ to 950 ℃, and the time of the heating is 3min to 6min.